Bcc metal hydride alloys for electrochemical applications

Abstract

BCC metal hydride alloys historically have limited electrochemical capabilities. Provided are a new examples of these alloys useful as electrode active materials. BCC metal hydride alloys provided include a pressure plateau in the desorption PCT isotherm measured at 30° C. with center between 0.1 MPa and 1.0 MPa, and/or a plateau region between 0.05 weight percent to 0.5 weight percent of H 2 . This pressure plateau represents a new catalytic phase capable of producing increased capacity in the absence of additional catalytic phases.

1 . A BCC metal hydride alloy comprising a pressure plateau with center at or between 0.1 MPa and 1.0 MPa and a plateau region between 0.05 weight percent to 0.5 weight percent of H 2  in the desorption PCT isotherm measured at 30° C. 
     
     
         2 . The alloy of  claim 1  wherein said equilibrium pressure plateau has a center between 0.2 and 0.5 MPa and the plateau region is between 0.05 weight percent to 0.5 weight percent of H 2 . 
     
     
         3 . The alloy of  claim 1  wherein said equilibrium pressure plateau has a center between 0.2 and 0.5 MPa and the plateau region is between 0.1 weight percent to 0.3 weight percent of H 2 . 
     
     
         4 . The alloy of  claim 1  free of electrochemically active secondary phase. 
     
     
         5 . The alloy of  claim 1  comprising an initial capacity of 70 milliampere hours per gram or greater. 
     
     
         6 . The alloy of  claim 1  comprising a modifier effective to enlarge the unit cell. 
     
     
         7 . The alloy of  claim 6  wherein said modifier is B, Zr, Mo, Nb, or combinations thereof. 
     
     
         8 . The alloy of  claim 1  comprising the composition of Formula I:
   Ti w V x Cr y M z    (I)
 
 
       where w+x+y+z=1, 0.1≦w≦0.6, 0.1≦x≦0.6, 0.01≦y≦0.6, and M comprises an element selected from the group consisting of Mn, Al, Si, Sn, and transition metals. 
     
     
         9 . The alloy of  claim 8  wherein M comprises Mn. 
     
     
         10 . The alloy of  claim 8  wherein M further comprises a modifier selected from the group consisting of B, Zr, Mo, Nb, or combinations thereof. 
     
     
         11 . The alloy of  claim 1  comprising a composition of Formula II:
   Ti 40 V 30 Cr 15 Mn 13 X 2    (II)
 
 
       where X═B, Zr, Nb, or Mo. 
     
     
         12 . The alloy of  claim 10  where X is Mo. 
     
     
         13 . The alloy of  claim 10  where X is B. 
     
     
         14 . The alloy of  claim 10  where X is Zr. 
     
     
         15 . A metal hydride alloy comprising greater than 90 percent BCC phase and a capacity 60 milliampere hours per gram or greater measured at 25 degrees Celsius. 
     
     
         16 . The metal hydride alloy of  claim 15  comprising greater than 95 percent BCC phase. 
     
     
         17 . The metal hydride alloy of  claim 15  comprising greater than 99 percent BCC phase. 
     
     
         18 . The metal hydride alloy of  claim 15  wherein said capacity is 100 milliampere hours per gram or greater measured at 25 degrees Celsius. 
     
     
         19 . The metal hydride alloy of  claim 15  wherein said capacity is 200 milliampere hours per gram or greater measured at 25 degrees Celsius. 
     
     
         20 . The metal hydride alloy of  claim 15  comprising a pressure plateau with center between 0.2 MPa and 0.5 MPa in the desorption PCT isotherm measured at 30° C.